Electrostatic spraying apparatus



SePf- 15, 1964 M. A. R. POINT 3,148,831

ELEcTRosTATIc SPRAYING APPARATUSE Filed 0G13. 13, 1961 A ttarneyg,

United States Patent O 3,148,831 ELECTROSTATIC SPRAYING APPARATUS Marcel Auguste Roger Point, Grenoble, France, assignor to Societe Anonyme de Machines Electrostatiques, Grenoble, France, a French body corporate Filed Oct. 13, 1961, Ser. No. 145,024 Claims priority, application France Oct. 17, 1960 6 Claims. (Cl. 239-15) The present invention has for an object an improvement in rotary head electrostatic guns combining atomisation by centrifugal force and atomisation by electrostatic forces.

In previously known guns, the paint feed pipe located between the pistol grip and the nozzle which supplies this paint to the rotary head is generally straight or sometimes wound in a helix about the portion forming the barrel of the gun.

It has in fact been noted that with so-called metallic paints, i.e. paints containing metallic particles in suspension, a straight paint feed pipe could give rise to operational ditliculties caused by the electrical conductivity of the metallic pigments which become deposited in the bottom of the straight feed pipe.

In order to avoid these difficulties it has already been proposed to lengthen this pipe by making it, at least over a portion of its length coiled in the form of a helix, preferably with continguous spirals, either about the barrel of the gun or about a separate support.

It has now been found by tests that it is not so much the lengthening of the feed pipe which is effective in such a device, as the fact that the metallic pigments have a tendency to form a sediment at the lowest points in the spirals.

On the other hand the pipe or tube which is thus wound in a helix occupies a considerable volume and leads to a heavy and unwieldy apparatus.

In order to remedy these drawbacks and according to the present invention, the paint feed pipe, at least over a portion of its length, is made in the form of a sinuous tube the bends of which are arranged in the same plane, which allows this tube to be mounted on any suitable flat support.

Moreover, the bends are arranged so as to form considerable and numerous interruptions in the final deposit of conductive metallic pigments, these interruptions being formed due to the presence in the tube of numerous nonhorizontal portions which are also as Vertical as possible and by avoiding horizontal portions.

In order better to show the technical characteristics and advantages of the invention, a preferred embodiment will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGURE l shows an elevation partly in section of an electrostatic gun comprising a paint feed pipe according to the invention, and

FIGURE 2 is a transverse section of the barrel of this gun on the line 2-2 in FIGURE l, viewed in the direction of the arrows.

Referring to the drawings, the gun comprises a butt 10 supporting at its rearward end a small electric motor 11 which can rotate an insulating driving shaft 12 located within the insulating barrel 13 of the gun at high speed. The forward end of the shaft 12 is firmly secured by any suitable means to a rotary atomising head 14 of any known type.

In order to simplify the drawing, the current conductors for the motor 11 have not been shown, nor has the high voltage cable connected to the head 14. These parts enter the lower portion of the butt 10. FIGURE 2 however shows the passage 22 in the barrel for the high voltage cable.

Patented Sept. 15, 1964 A trigger 15 with a return spring and an adjusting knob 16 has been shown in a diagrammatic way, said knob allowing the quantity of paint arriving at the end 17 of the paint feed pipe to be regulated. The paint is projected into the head 14 by an injector or nozzle 18 which extends into this head without interfering with its rotation.

According to the present invention, the paint feed pipe comprised between the part 17 and the injector 18 is constituted by an insulating sinuous tube 19, supported for example on insulating pegs such as 20 which are either firmly secured to the insulating barrel 13 or form an integral part thereof. As may easily be seen in FIGURE 2, all the curves or bends of the insulating tube 19 are arranged in the same plane against a ilat vertical surface of the barrel.

Furthermore FIGURE l clearly shows that this tube comprises many non-horizontal portions which are as vertical as possible. Thus, inside the tube are effected numerous and considerable interruptions in any deposit of metallic pigments at the low points in the spirals.

It may also be seen that the increase in the length of the tube 19 as against a straight tube is relatively small, and much smaller than the lengthening which would result from the coiling of the tube in a helix about the barrel of the gun. The sinuous tube 19 does not increase the volume of the barrel and only increases its weight to an insignificant degree, while bringing with it the advantages mentioned above.

An insulating protection cover 21 of any suitable type is fixed to the barrel 13 and helps to maintain the tube 19 in place in the barrel.

A hook 23 may be fixed to the butt 10 in order to hang the gun up when it is not being used.

Although only a preferred embodiment of the invention has been described and shown, it is obvious that detailed variations can be applied thereto without departing from its scope.

Thus for example the tube 19 has been shown in a substantially sinusoidal shape, but it is obvious that this tube can, for example, be in the form of crenellations, in Greek key patterns or again of a saw-tooth shape, or any other equivalent shape which causes considerable and numerous interruptions in any deposit of metallic pigments which may occur.

I claim:

l. A spray gun for the electrostatic spraying of finely divided materials composed of conducting particles, such as metallic paints, and having a butt and a barrel, a paint feed pipe of electrically insulating material extending in a direction generally parallel to the longitudinal axis of said barrel and comprising a sinuous tube located within said barrel and having its bends all lying in a common plane which extends parallel to the longitudinal axis of said barrel and from top to bottom of said barrel whereby the bends of said tube are disposed in a substantially vertical plane when the gun is held in the position of use.

2. A spray gun as claimed in claim l, including means for supporting said sinuous tube in position within the barrel of the gun.

3. A spray gun as claimed in claim 2, wherein said bends have a sinusoidal shape.

4. An electrostatic spray gun for depositing on objects a nely pulverized electrically conducting fluid material, such as metallic paint, said spray gun having a barrel, a rotary spraying head mounted at one end of said barrel, a nozzle for delivering said material to the rotary head, and means for feeding said fluid material to said nozzle comprising a sinuous tube of electrically insulating material located within and extending longitudinally of said barrel and having its ben'ds all lying in the same plane which extends parallel to the longitudinal axis of said barrel and from rtop to bottom of said barrel whereby the 3 bends of said tube are disposed in a substantially vertical plane when the gun is held in the position of use.

5. A spray gun for the electrostatic spraying of finely divided materials composed of conducting particles, such as metallic paints, and having a butt and a barrel, a paint feed pipe of electrically insulating material extending in a direction generally parallel to the longitudinal axis of said barrel and comprising a sinuous tube located within said barrel and having its bends all lying in a common plane which extends parallel to the longitudinal axis of said barrel and from top to bottom of said barrel whereby the bends of `said tube are disposed in a substantially vertical plane when the gun is held in the position of use, and means for supporting said sinuous tube in position Within the barrel of the gun comprising a at surface extending longitudinally of the barrel of the gun and provided with a plurality of supports around which said sinuous tube successively passes so as to form the bends which have a large number of non-horizontal surfaces when the gun is held in the position of use.

6. An electrostatic spray gun for depositing on objects a finely pulverized electrically conducting fluid material,

such as metallic paint, said spray gun having a barrel, a rotary spraying head mounted at one end of said barrel, a

nozzle for delivering said material to the rotary head,V

means for feeding said fluid material to said nozzle comprising a sinuous tube of electrically insulating material located Within and extending longitudinally of said barrel and having its bends all lying in the same plane which extends parallel to the longitudinal axis of said barrel, and supporting means for holding said sinuous insulating tube comprising a flat surface provided longitudinally Within the barrel of said gun and which is arranged s0 that said bends are disposed in a generally vertical plane when the gun is in its position for use.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A SPRAY GUN FOR THE ELECTROSTATIC SPRAYING OF FINELY DIVIDED MATERIALS COMPOSED OF CONDUCTING PARTICLES, SUCH AS METALLIC PAINTS, AND HAVING A BUTT AND A BARREL, A PAINT FEED PIPE OF ELECTRICALLY INSULATING MATERIAL EXTENDING IN A DIRECTION GENERALLY PARALLEL TO THE LONGITUDINAL AXIS OF SAID BARREL AND COMPRISING A SINUOUS TUBE LOCATED WITHIN SAID BARREL AND HAVING ITS BENDS ALL LYING IN A COMMON PLANE WHICH EXTENDS PARALLEL TO THE LONGITUDINAL AXIS OF SAID BARREL AND FROM TOP TO BOTTOM OF SAID BARREL WHEREBY THE BENDS OF SAID TUBE ARE DISPOSED IN A SUBSTANTIALLY VERTICAL PLANE WHEN THE GUN IS HELD IN THE POSITION OF USE. 